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Uses and fonctions of fallow in tropical- and NW-Afïican production systems |
Cahiers Agricultures. Volume 2, Number 5, 308-17, Septembre-Octobre 1993, Synthèse
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 Résumé
Article gratuit
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Author(s) : Philippe Jouve |
Summary : Fallow is an age-old farming-practice still used extensively in developing countries. How it is done varies from one region to the next according to the corresponding production systems. Its uses and fonctions are analysed for three major agro-ecological zones of Africa. In sparsely populated regions of the rainy tropics, the land is used according to an itinerant crop system. After a long period of fallow, the tree-bearing land is cleared by slash and burn, and crops are planted or sown. The fallow ensures the mineral elements are recycled and concentrated in the soil’s superficial horizons, thus playing an important role in keeping the milieu fertile. But it also plays an equally important role in controlling weeds. Letting tree-bearing land lie fallow results in the gradual extinction of weeds which considerably limits the need for weeding the crops for the first 2 to 3 years after clearing. But the very characteristics of this system make it resistant both to change and the increase in land-use resulting from population growth. In Sudano-Sahelian production systems, the primary function of fallow is to ensure the continued physical and chemical fertility of the soil. This therefore requires fallow periods long enough to allow grasses and shrubs to grow, and results in vertical transfer of minerals and an increase in the soil’s organic matter level, which tends to drop every time the land is sown or planted. The increasing demands on land, particularly high in this region, result in a shortening of fallow period which considerably reduces its role in maintaining fertility. Fallow thus becomes used mainly for forage. Forage is also the main function of fallow in the Maghreb. In production systems combining crops and stock-breeding, where growing forage is still little developed, forage fallow still tends to be used on both large and small farms. Fallow in North Africa may also be used to ensure water storage from one year to the next. However, this function requires environmental conditions and practices (laboured fallow) limiting both the possibility and profitability of so doing. |
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